Unless otherwise indicated herein, approaches described in this section are not prior art to the claims listed below and are not admitted as prior art by inclusion in this section.
There are various well-developed and well-defined cellular communications technologies in telecommunications that enable wireless communications using mobile terminals, or user equipment (UE). For example, the Global System for Mobile communications (GSM) is a well-defined and commonly used communications system, which uses time division multiple access (TDMA) technology, which is a multiplex access scheme for digital radio, to send voice, video, data, and signaling information (such as a dialed telephone number) between mobile phones and cell sites. The CDMA2000 is a hybrid mobile communications 2.5G/3G (generation) technology standard that uses code division multiple access (CDMA) technology. The UMTS (Universal Mobile Telecommunications System) is a 3G mobile communications system, which provides an enhanced range of multimedia services over the GSM system. The Long-Term Evolution (LTE), as well as its derivatives such as LTE-Advanced and LTE-Advanced Pro, is a standard for high-speed wireless communication for mobile phones and data terminals. In addition, there are some newly developed next generation communication technologies such as 5th Generation (5G), New Radio (NR), Internet of Things (IoT) and Narrow Band Internet of Things (NB-IoT). These communication technologies are developed for higher speed transmission and serving for huge number of devices including machine type devices.
In some communication systems, short message service (SMS) may be provided for transmitting messages between the UE and the network apparatus. When transmitting the short messages, the signal transmission or the channel condition between the UE and the network apparatus may temporarily become bad or have some problems. The short message may not be well received at the other side or may be lost in the first transmission. However, the channel condition between the UE and the network apparatus may recover in a short time. Without proper re-transmission mechanisms, the short message service may be considered as failed or unsuccessful.
Accordingly, it is important for the UE and the network apparatus to properly perform short message re-transmission. Therefore, in developing communication systems, it is needed to provide proper mechanisms for the UE and the network apparatus to perform re-transmission for short message services.